Cylinder Texturing problem
In your case, what I would do is delete all but one "tile" of the barrel, then make it a circular array.



Below you can see the Empty inside being used by the Array Modifier. It is rotated 11.25° (360° / 32 tiles).
Enabling "Merge" on the modifier means the tiles will be connected when the modifier is applied.



UV unwrap before applying your modifier.